LONDON (Reuters) - OPEC could announce a 500,000 barrels per day output hike within two weeks if oil prices stay above $55 for at least the next 10 days to 14 days, Nigerian Presidential Adviser on Petroleum Edmund Daukoru said on Sunday. "I think we will take the decision shortly if the price stays above $55 for 10 days or two weeks," Daukoru told Reuters in an interview. "I think the decision can be announced within two weeks." OPEC chief Sheikh Ahmad al-Fahd al-Sabah said on Saturday he was likely to start telephone consultations with the group's oil ministers on...